1. Field Of The Invention
The present invention relates to apparatus having blades for cutting through a layer coating material on a filamentary core, and for stripping the severed material fully or partly from a terminal end of the core. For example, the apparatus may operate upon an electrical wire to sever and strip a slug of insulation from the end of the conductor. More particularly, a principal aspect of the invention concerns improvements in such apparatus providing automatic adjustment of the clamping force applied to the wire to prevent axial movement thereof as the insulation is severed and stripped; another aspect of the invention relates to the means for mounting and reciprocally moving the cutting blades. Other features of the invention relate to improvements in the construction and relative arrangement of elements of pneumatically operated wire insulation cutting, severing and stripping apparatus.
2. Related Prior Art
Many forms of both manually and power operated apparatus have been provided for high volume severing and stripping of coating layers from filamentary core materials such as electrical wires and optical fibers. An example of manually manipulated apparatus of this type, including means for gripping the wire as a pair of blades move radially of the wire to cut the insulation and then axially to strip the severed slug of insulation from the conductor, is described in U.S. Pat. No. 2,313,793 of Wood. Electrically powered apparatus for performing similar operations is found in U.S. Pat. Nos. 4,933,147 and 4,933,287 of Carpenter et al. Pneumatically and combined electrically-pneumatically powered apparatus of this type is also commercially available.
One of the requirements of such apparatus is that the workpiece must be restrained against axial movement as an axial force is applied to the coating material which is to be separated from the remaining material. The most common means employed to restrain axial movement of the workpiece is a pair of gripping or clamping members between which the workpiece is firmly engaged as the axial force is applied. The gripping force applied to the workpiece, which may be provided, e.g., by spring biasing the clamping members toward a closed position, must be great enough to prevent axial movement of the workpiece when the greatest axial force contemplated during normal operation is applied. Thus, the radial clamping force is often greater than that which would actually be required for a given severing and stripping operation, and raises the possibility of damage to the workpiece.
In addition, although it is often expedient to provide the gripping force through a pair of pivotally mounted clamp arms, difficulties are sometimes experienced with such arrangements. Since the apparatus is preferably suitable for operating upon workpieces of different diameters, the opposed clamping surfaces of pivotally mounted arms will assume different angular relationships to one another when engaging different workpieces. This may exert an undesirable radial force on the workpiece, particularly when relatively high gripping forces are applied, i.e., the workpiece may slip on the gripping surfaces and/or be damaged thereby. It is therefore desirable to provide clamping means which retain the advantages of pivotal mounting while engaging the workpiece between reciprocally moveable surfaces which remain parallel during such movement.
While some apparatus of the type under consideration employs rotating blade means to cut entirely around the workpiece, others use a pair of blades having V-shaped cutting edge cooperatively defining a four-sided aperture with means for reciprocally moving the blades radially of the workpiece. Although the most mechanically expedient means for mounting the blades is often for pivotal movement, it is more difficult to maintain precise alignment of pivotally than of linearly reciprocating blades. It is also necessary, in either case, to provide linearly reciprocating movement of the blades axially of the workpiece to complete severing of the coating material and stripping the severed slug fully or partially from the terminal end of the core. Thus, there exists a need for convenient and economical blade mounting means which also ensure precise blade alignment.
Some prior art apparatus utilizes a single motive means, e.g., a pneumatic cylinder, intended after a single actuation to provide sequential motion to elements of the apparatus. The clamping arms must be moved first in order to grip the workpiece, the blades are then moved radially of the workpiece to cut through the outer layer, and the blades are then moved axially of the workpiece to complete severing and stripping of the severed slug from the inner core. Frictional drag means are provided to inhibit movement of the blades until the workpiece is firmly clamped. Although spring tension means may be employed for selective adjustment of the frictional force opposing movement of blades axially of the workpiece, reliability of operation would be enhanced by means which lock the blade movement elements in place until a predetermined force is applied.